Interesting stuff....the crank seals have that tiny spring that encircles the I.D. part of the seal, that seals against the crankshaft. If you flip it around, won't this spring now be exposed to the elements (dust, dirt, moisture) rather than being continuously bathed by the 2 stroke oil passing thru the internal side of the motor? I'm sure it would work...for awhile....until the spring craps out.
Since it's on the mag end, it's buried behind the recoil, the flywheel, the stator....you would never see the seal again until the next rebuild. On the PTO end you could at least pop the drive clutch once in awhile to check the seal and spring...and maybe squirt a little oil on the spring to keep it from rusting.
I can't remember, without tearing into my Kawi, if it's seals have that spring on only the one side....I remember one motor I worked on long ago had 2 springs on the crank seal...both inside and out.
It would be like searching for a needle in a haystack....but ya just know there is a crank seal out there that has the same O.D. as the Kawis....but has a millimeter or 2 smaller I.D.....that would be the berries....a machine shop could spin the pitted area on the crank down to the new dimension and you would be good to go.
You would have to attach a note if you ever sold the sled.....some poor bugger would be on this site asking why he keeps seizing a piston after installing new (stock) crank seals!!